First, it's normal for tires to get beat up at a track day, so don't give up on your tires.

I'd probably use them up then buy a new set rather than throw them away.

As for track tires, I wouldn't go to R compounds, just get a good summer tire like Michelin Pilots, Bridgestone SO3 (SO4?) etc. R compounds will have more grip but will let go suddenly, you don't learn as much as with a tire that gives up more progressively.

 

If you want a good street/autocross/track tire - keeping in mind it will be grippy only in the warmer (above ~45°) months - take a look at Dunlop Direzza ZII's. They're the new Dunlop Star Spec and they are a good all-rounder summer tire.

 

Good information. The problem is that the rear RFTs are in new condition while the fronts will be finished with another track day. I don't want to replace the fronts with RFTs, I want to eventually move away from RFTs altogether. So short of throwing out or selling both new rear tires and getting a full set of Dunlops or Michelins I haven't come up with a solution yet. Also I want to research if I can go up a size on the new tires without running into any body intereference issues. So I am also looking for the best tire that will tolerate occasional track day beatings down here in Florida/Georgia.
All while trying to explain to my wife why "her" car needs new tires so soon.

 

Rotate them, you'll have a blast on the track with 255 fronts and 225 rears.

This is why BMW's 225 front, 255 rear setup sucks. Can't rotate them, and the fronts are too narrow. Go 235s front and back, probably solved.

 

I think that you are right. Best solution would be to get Bridgestone Potenza S-04 or Dunlop Direzza Z11 in 235/40R18 all round. Thanks

 

I just wonder why BMW went the 215 front/245 rear in the first place? Handling balance?

 

That's not balanced, they wanted safe understeer. The 1 series with it's short wheelbase and powerful engine is more tricky to drive than a 3 series.